README.md

bit_utils

Utils for binary operation. Main contains two utils: BitBuffer and BinStringHelper.

---

BitBuffer

A buffer wrapped java.nio.ByteBuffer, provide operate a buffer in bit unit. Functions like ByteBuffer.

• You can use wrap a byte array to create BitBuffer. Then you can get some bits from it. Simplified usage like below:

  byte[] data = { (byte)210, 50 }; // 11010010  00110010
  BitBuffer buffer = BitBuffer.wrapBytes(data);
  
  System.out.println(buffer.remainingBits()); // 16
  
  byte bit = buffer.getByte(2); // get 2 bits, return in a byte.
  // This bit is 3.
  
  System.out.println(buffer.remainingBits()); // 14
  
  bit = buffer.getByte(7,8); // This means get 8 bits from 7 position, return in a bytes.
  // This bit is 25(00011001).
  
  System.out.println(buffer.remainingBits()); // 14, not change.
  
  // or  byte[] bits = buffer.getBytes(12); // This means get 12 bits, return in 2 bytes.
  // This bits is {210, 3}
  

• You can use allocate fix capacity to create empty BitBuffer. Then you can put some bits in it. Simplified usage like below:

  byte data = (byte)9; // 1001
  BitBuffer buffer = BitBuffer.allocate(20);
  buffer.put(data, 4); // now buffer is 1001
  
  System.out.println(buffer.remainingBits()); // 16
  
  byte[] datas = new byte[]{ (byte)210, 89 }; // 11010010 01011001
  buffer.put(datas, 15); // This means put 15 bits into buffer, buffer is 10011101 00100101 100
  
  System.out.println(buffer.remainingBits()); // 1
  
  buffer.put(data, 2, 4); // This means put 4 bits into buffer, start position is 2
  // now buffer is 10100101 00100101 100
  
  System.out.println(buffer.remainingBits()); // 1, not change.
  
  buffer.flip();
  
  System.out.println(buffer.remainingBits()); // 19
  

More usage in doc and test.

---

PickBitsHelper

A simple tool to pick some bits from number.

Example: pickBitsPartOfByte(data, 2, 5); If data is 10010011(binary), will pick bits 01001(binary), return byte is 0x09.

---

BinStringHelper

A simple tool, provide some static function to change number(byte,byte[],int,short,long) to a binary string. Usually used to print for debug.

Example:

• byte 210 -> "11010010 "
• int -1 -> "11111111 11111111 11111111 11111111 "